Architectural Record BE - Building Enclosure

Delivering Architectural Aesthetics and Sustainability with Extruded Aluminum Trim

Extruded aluminum trim can add architectural distinction to both the interiors and exteriors of a wide range of building types as well as complement moisture management systems
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Sponsored by TAMLYN
By Karin Tetlow

Trim Finishes

Extruded aluminum trim is typically available in standard color finishes or primed ready to paint, and also in anodized finishes.

Precolored

Manufacturers recommend one of the standard palette colors because each is made to the exact standards of the largest U.S. cementitious siding manufacturer. The fully engineered paint-coating system is computer matched, fade resistant, uses no volatile organic compounds (VOCs), and is expected to last eight years.

Custom Color

Design professionals requiring custom colors can specify a primed ready-to-paint finish. Manufacturers typically provide a painting guide and recommend following a paint manufacturer’s instructions for an eco-friendly, sustainable, recyclable, fire-resistant, direct-to-metal (DTM) paint material. Aluminum does not rust. It can, however, corrode if its protective coating is uncovered. Manufacturers recommend recoating trim after making end cuts or if there are surface scratches.

Example of custom-patterned extruded aluminum trim.

Photo courtesy of TAMLYN

Examples of custom-patterned extruded aluminum trim

Custom Pattern

Design professionals can also order trim in a custom pattern. In one example in an airport interior, the wallpaper pattern was repeated on the aluminum trim covering panel joints in order to provide a continuous unbroken appearance.

Clear Anodized Finish

A clear anodized finish is an electrochemical conversion process that deposits an oxide film on the aluminum trim. While a natural oxidation process occurs on bare aluminum, producing the controlled oxidation process artificially creates a thicker, harder, and more durable “oxide film.” Clear anodized is an extremely durable finish and is resistant to most forms of corrosion. Design professionals should note that clear anodized finishes can vary slightly from one piece of trim to another and should consider this characteristic before ordering.

Special Color Anodized Finishes

Manufacturers also offer special color anodized finishes if required. Typical colors are gold, black, and bronze. Again, design professionals should note that finishes can vary from one piece of trim to another. Typically, the color of the anodizing will fall within a certain range, which usually can be determined prior to anodizing. The manufacturer should provide anodized color details upon request. Specifiers should require that anodized coating thickness be tested in accordance with ASTM B244-68.


Keeping Moisture Out

Walls with cladding leak just like masonry walls and must drain and dry moisture since water is the most significant factor in the premature deterioration of buildings. Leakage paths exist at any opening in the wall surface, whether intended or unintended. Joints between materials and around windows and doors, vents, cracks, and porous surfaces are all potential entry points for water. As mentioned above, trim manufacturers either recommend or offer moisture management products that help meet code requirements.


Code Requirements

The International Residential Code (IRC) 2015 states: “Section R703 Exterior Covering: R703.1 General. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing as described in Section R703.4. The exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer as required by Section R703.2 and a means of draining to the exterior water that enters the assembly. R703.4 Flashing. Approved corrosion-resistant flashing shall be applied shingle-fashion in a manner to prevent entry of water into the wall cavity or penetration of water to the building structural framing components. Self-adhered membranes used as flashing shall comply with AAMA (American Architectural Manufacturers Association) 711. The flashing shall extend to the surface of the exterior wall finish.”


Housewrap and Rainscreens

Exterior walls performance requirements are included in the 2015 ICC Section 1403.2: “Weather protection: Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in Section 1405.4 The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, as described in Section 1404.2, and a means for draining water that enters the assembly to the exterior. Protection against condensation in the exterior wall assembly shall be provided in accordance with Section 1405.3. (1405.3 Vapor retarders as described in Section 1405.3.3 shall be provided in accordance with Sections 1405.3.1 and 1405.3.2, or an approved design using accepted engineering practice for hygrothermal analysis.)”

Housewrap

The primary insurance of moisture mitigation for the building envelope is housewrap that is specifically designed to allow water or moisture to drain. There are several advantages to using an integrated wrap/drainage product. These include requiring no additional installation step and no design change to the wall/siding assembly. One type of housewrap on the market eliminates excess moisture from an exterior wall by providing drainage space between the housewrap and exterior sheathing. This is achieved by bonding very small spacers to the wrap.

Shown here is an example of a moisture management housewrap.

Photo courtesy of TAMLYN

Shown here is an example of a moisture management housewrap with 1.5-millimeter spacers that provide a drainage space between the sheathing and cladding material

Rainscreen

Another option for meeting code requirements is a rainscreen system. A rainscreen is a moisture management technique for controlling rain entry in an exterior wall. It generally comprises an air space immediately behind exterior cladding plus a water-resistive barrier that wraps the building wall assembly. The air space that is created by the rainscreen between the back of the cladding and the face of the water-resistive barrier is designed to reduce the forces that draw water into the assembly. Water that does reach the back of the cladding drains from the wall assembly via the space created by the rainscreen. In addition to the drainage capabilities, a rainscreen system also helps accelerate the drying of water vapor that accumulates in the interior wall assembly by moving air throughout the air space. There are several rainscreen options available, including:

Installing “weeps” in masonry construction. “Weeps” or “weeper holes” are small openings left in the outer wall as an outlet for water inside a building to move outside the wall and evaporate.

Constructing a rainscreen wall using furring strips that space the cladding away from the wall. This provides a vent space that helps to dry the back of the siding. Traditionally, layered tarpaper and flashing behind the furring strips created what is called a drainage plane. Now housewrap is more commonly used than tarpaper.

Rainscreen products can be batten strips in the form of plastic slats typically 11/2-inch by 1/2-inch placed on top of the housewrap.

Shown here is an example of a rainscreen strips product.

Image courtesy of TAMLYN

Shown here is an example of a rainscreen strips product used to create a cavity between the cladding and building wall assembly

The ICC 2015 Section 1405.4 states: “Flashing. Flashing shall be installed in such a manner so as to prevent moisture from entering the wall or to redirect it to the exterior. Flashing shall be installed at the perimeters of exterior door and window assemblies, penetrations and terminations of exterior wall assemblies, exterior wall intersections with roofs, chimneys, porches, decks, balconies and similar projections and at built-in gutters and similar locations where moisture could enter the wall. Flashing with projecting flanges shall be installed on both sides and the ends of copings, under sills, and continuously above projecting trim.”

Flashing

Aluminum has long been the flashing of choice because it is widely available, inexpensive, lightweight, and fairly easy to handle. A coil of aluminum trim coated on both sides with a paint system that is specifically formulated for residential applications will serve most residential and light commercial applications.

Precut and preformed profiles designed for siding, counter, brick ledge, window, and other areas have the advantage of being available in custom sizes and colors that match trim and siding.

Diagram showing aluminum butt joint flashing.

Image courtesy of TAMLYN

Aluminum butt joint flashing is precut and easily installed



Diagram showing aluminum butt joint flashing.

Image courtesy of TAMLYN

Shown here is an example of aluminum butt joint flashing with strips of EPDM rubber, which diverts water downward

Sustainability and LEED Credits

Beyond aesthetics and performance, extruded aluminum architectural trim can offer a number of sustainability features and environmental benefits. Extruded aluminum trim products are typically made from 75 to 100 percent post-industrial and post-consumer scrap. They can contribute to LEED credits in categories MR Credit 4: Recycled Content and, in some regions, MR Credit 5: Regional Materials of the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) certification, 2009 for New Construction and Major Renovations.

MR Credit 4: Recycled Content
1–2 Points
Intent: To increase demand for building products that incorporate recycled content materials, thereby reducing impacts resulting from extraction and processing of virgin materials. Requirements: Use materials with recycled content such that the sum of postconsumer recycled content plus half of the preconsumer content constitutes at least 10 percent or 20 percent, based on cost, of the total value of the materials in the project. The minimum percentage materials recycled for each point threshold is 10 percent recycled content for one point; 20 percent recycled content for two points.

MR Credit 5: Regional Materials*
1–2 Points
Intent: To increase demand for building materials and products that are extracted and manufactured within the region, thereby supporting the use of indigenous resources and reducing the environmental impacts resulting from transportation. Requirements: Use building materials or products that have been extracted, harvested or recovered, as well as manufactured, within 500 miles of the project site for a minimum of 10 percent or 20 percent, based on cost, of the total materials value.

*Note: MR Credit 5: Regional Materials applies only in Texas.


Conclusion

Available in a number of configurations, extruded aluminum trim can add architectural distinction to both the interiors and exteriors of a wide range of building types. Typically manufactured to work as a system with cementitious or fiber cement panel or lap siding, it is more convenient and easier to install than trim made from wood or fiber cement panels and saves labor time. Since aluminum is 75 percent to 100 percent post-industrial and post-consumer scrap, it is also sustainable and can contribute to LEED recycled content points. While it is critical that design professionals understand how to incorporate water and moisture management systems in building design, they should be aware that trim products by themselves do not necessarily include moisture management or insulation systems.



“Tamlyn

Tamlyn manufactures Xtreme Trim™, which consists of sustainable extruded aluminum profiles for fiber cement and other materials. Xtreme Trim™ profiles are designed to work together as a system to create an aesthetically attractive and durable appearance. www.xtremetrim.com

 

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